删除链表中重复元素

class :
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head == None or head.next == None:
            return head

        dummy = ListNode(0)
        dummy.next = head
        pre = dummy
        cur = dummy.next

        while cur != None:
            while cur.next and cur.next.val == pre.next.val:
                cur = cur.next
            if pre.next == cur:
                pre = pre.next
            else:
                pre.next = cur.next
            cur = cur.next
        return dummy.next

ll = creat_ll([1,2,3,3,3,3,4,4,5])
res = Solution().deleteDuplicates(ll)
print_ll(res)